The normal surface and exfoliation pattern of rabbit and rat corneal epithelium will be compared by scanning electron microscopy and transmission electron microscopy to the surface in various disease states. Animal models showing durg effects, dellen, induced hypovitaminosis A and reduced tear conditions will be studied. In addition, corneal surface changes will be evaluated after infection, trigeminal neuronectomy and cold exposure. Regeneration of corneal epithelium after abrasion and alkali burns will also be studied. The pattern of normal corneal exfoliation in the primate, including man, will be studied and compared to the pattern already described in the rabbit. Emphasis will be placed on the clinical implications of these anatomical studies.